This invention is concerned with a blood lancet system for blood withdrawal for diagnostic purposes.
In case of various illnesses it is necessary to investigate the human blood with respect to a component (analyte) contained therein. To this end it is oftentimes sufficient to withdraw a small amount of blood from the body by generating a small prick wound. A particularly important such case is diabetes mellitus, which requires the blood to be investigated in regular intervals for its glucose content.
For generating the necessary prick wound, commonly blood lancet systems are used which comprise a pricking apparatus and replaceable lancets, adapted to this apparatus. The housing of the pricking apparatus contains a lancet adapted for holding the lancet in a replacable manner. During the pricking process, the lancet is driven by a lancet drive, also integrated in the lancet apparatus, in a way that the lancet is moved quickly in the pricking direction, until the lancet tip protrudes from an opening at the front end of the pricking apparatus, thus generating a small prick wound in the body part pressed against the front end. Thereafter the lancet is moved back (against the pricking direction).
When common pricking apparatuses are in their use state, the lancet holder is covered by a housing cap which forms the front end of the pricking apparatus housing and has a small opening through which the lancet tip can protrude during the pricking process. The pricking opening is surrounded by a contact surface which serves for contacting the blood lancet apparatus to the body part from which the blood shall be withdrawn during use of the blood lancet apparatus (usually the finger tip or the ear lobe).
For avoiding infections, the lancets are disposable elements designed for a single use. In order to insert a new lancet, the housing cap covering the lancet holder is removed, and the lancet is inserted into the lancet holder. The housing cap is also removed for removing used lancets.
Blood lancet systems are not only used by medical staff, but also, and to a large extent, by non-experts. This is particularly true for the therapy control of diabetics. It was determined that serious damages occurring in conjunction with diabetes (e.g. blindness) can be dramatically reduced if the glucose concentration of the diabetic""s blood is measured very often (four to five times a day), adjusting the insulin injections very exactly, using these measurements. The willingness and the ability of diabetics to check their blood that often in the scope of home-monitoring highly depends on the optimal function of the blood lancet system used.
An important part of this function are the handling steps necessary for the insertion of new and the removal of used lancets. On one hand, they should be as simple as possible, and on the other hand there should be maximum safety against injury and infection risks. At the same time, the cost, in particular with respect to the disposable material, should be as low as possible.
During the insertion of the lancet, the sharp tip of the lancet needle is usually covered by a tip cover element made of plastic and allowing a secure handling of the lancet. Once the lancet is inserted, the tip cover element must be removed and the housing cap must be attached. After the pricking process, the housing cap must be removed, so that the lancet becomes accessible again. Then, the lancet can be manually removed. The risk of injury at the lancet tip, however, is very high, in particular taking into account that a large share of the users is handicapped by high age, bad vision or trembling hands.
In order to simplify the removal of the used lancet, many apparatuses are equipped with a manually operated ejection mechanism. For example, U.S. Pat. No. 5,318,584 describes a blood lancet system in which the blood lancet can be ejected from the lancet holder by means of an ejection rod; the ejection rod is actuated by pressing an actuation button provided at the rear end of the pricking apparatus. U.S. Pat. No. 4,442,836 describes an apparatus having an ejection mechanism designed in a way that the used lancet is automatically thrown out when re-cocking the apparatus after each pricking process. However, such ejection mechanisms require a relatively complicated and expensive construction. The handling is not as easy as desirable, taking into account the health state of many users.
EP 0 958 783 A1 describes a blood lancet apparatus which is equipped with so-called engagement means at the cap, which can be moved by the user from a first position, not in engagement with the lancets, into a second position, where they contact the lancet pressing it against the opposite interior wall of the cap. For actuation of the engagement means, a button may be provided which protrudes laterally from the cap. After the pricking process the user must first press this button, thus clamping the lancet in the cap, then take off the lancet together with the cap, and finally dispose the lancet. This requires an additional, difficult handling step, causing a severe problem for many users.
With the aim to achieve optimal simplicity and operational safety some known blood lancet systems have the lancet integrated into the cap, so that the lancet and the housing cap together form a replaceable, disposable unit. Such designs are described in EP-0595148 A1 and in U.S. Pat. Nos. 4,990,154 and 5,628,765. A disadvantage of this design is the high material consumption, because the entire disposable design unit, including the housing cap, has to be disposed after each use. Due to the high cost these systems are only appropriate for application areas with high safety and hygienic requirements, in particular for the use in hospitals. In the home-monitoring area, on one hand safety risks are lower since the blood lancet systems are always used by the same patient, on the other hand the cost for the integrated lancet-cap-disposables is not acceptable.
On this basis, the invention addresses the problem to provide a blood lancet system, in particular for home-monitoring, which allows a riskless and simple removal of used lancets from the lancet holder without a need to touch the lancet and with as little expense as possible.
This problem is solved by a blood lancet system for blood withdrawal for diagnostic purposes, comprising lancets and a pricking apparatus with a housing, a lancet holder movable in the housing for holding an exchangeable lancet, and a lancet drive for driving a pricking movement of the lancet on a predetermined pricking path, wherein the housing comprises a cap to be attached at a forward end thereof in pricking direction, the cap being removable for removing a used lancet out of the housing, and the lancet and the cap are coupled to each other, while the cap is attached to the housing, by a coupling mechanism comprising coupling elements matched to each other, thereby enabling the extraction of the lancet from the lancet holder simultaneously with removing the cap.
In contrast to the mentioned lancet-cap-disposables, the lancet used with the instant invention is a separate element, produced and distributed independently from the housing cap. It is the only disposable part. The cap can be used permanently, thus it can be produced with higher quality. The use is very simple as the pulling-off of the housing cap and the removal of the used lancet is performed in a single handling step.
In contrast to the design described in EP 0958783, the invention does not require any additional handling steps, as the coupling of the cap with the lancet is performed automatically during the procedure of the handling steps which are anyway necessary and common.
In the most simple case, the coupling mechanism acts directly between the housing cap and the lancet. Generally, lancets have a lancet body made of plastic, surrounding the metal lancet needle. The first of the matched coupling elements can be provided at this lancet body. The second coupling element is provided, preferably, directly at the cap (at its inner wall). For example, the lancet body may have a groove-type recess running in the direction of its longitudinal axis, in which a catch may latch in, which latch protrudes from an elastic tongue fixed at the inside wall of the cap. When the cap is attached, the protruding catch latches into the groove. The dimensions of the groove are designed in such a way that the lancet movement in pricking direction, required for the pricking process, is possible.
An embodiment in which the coupling mechanism includes an additional part designated as ejector, is preferred. The ejector is arranged in the housing in a way that it is movable in the pricking direction. It is provided with a lancet contact element which contacts the lancet during the ejection process, thus pressing or pulling it out of the holder. For this design type, a first of the matched coupling elements is arranged at the ejector, and, preferably, a second of the matched coupling elements is arranged at the cap.